ABSTRACT Charcot Marie Tooth disease (CMT) is the eponym for heritable peripheral neuropathy. It is one of the most common inherited neuromuscular diseases, affecting approximately 1 in 2500 people. CMT can be classified into three large subgroups: CMT1 (dominantly inherited demyelinating neuropathies) CMT2 (the dominantly inherited axonal neuropathies), and CMT4 (the recessively inherited neuropathies). Genetically authentic animal models exist for many forms of CMT1, 2, and 4, and have provided the data compelling the clinical trials in humans currently underway for CMT1A. Despite these advances, there are no effective therapies for any form of CMT, natural history data are available for only the most common types (CMT1A and CMT1X), and many potential genotype-phenotype correlations remain unknown. The lack of knowledge about their natural history limits the clinical trials for most forms of CMT. To address this problem, we will use the resources in the Inherited Neuropathy Consortium to perform natural history evaluations of three most common forms of CMT that lack natural history data;CMT1B, CMT2A, and CMT4A.